Working with Forms and Controls in VB.NET KeyPress Event

The KeyPress event in VB.NET is an event that occurs when a key is pressed while the focus is on a control. This event is useful for handling input from the user, such as validation or formatting of input data.

Syntax

Private Sub control_KeyPress(sender As Object, e As KeyPressEventArgs) Handles control.KeyPress
    ' code
End Sub

Here, control is the name of the control that the event is being handled for.

Example

Private Sub txtName_KeyPress(sender As Object, e As KeyPressEventArgs) Handles txtName.KeyPress
    If Not Char.IsLetter(e.KeyChar) AndAlso Not Char.IsControl(e.KeyChar) Then
        e.Handled = True
    End If
End Sub

Output

The output of the above code will be that the KeyPress event will handle the input of the txtName control, allowing only letters and control keys to be entered.

Explanation

In the above example, we have a txtName control that we want to validate to ensure that only letters are entered into the field. We handle the KeyPress event for the control and check if the pressed key is a letter or a control key. If it is not, we set the e.Handled property to True, which prevents the key from being entered into the control.

Use

The KeyPress event can be used to enforce input validation and formatting for controls in a VB.NET application. For example, you could use this event to ensure that a field only accepts numbers or dates in a specific format.

Important Points

• The KeyPress event in VB.NET allows you to handle input from the user while a control has focus.
• You can use this event to enforce input validation and formatting for controls in a VB.NET application.
• The e.KeyChar property of the KeyPressEventArgs object contains the character that was pressed.
• The e.Handled property of the KeyPressEventArgs object can be used to prevent the character from being entered into the control.

Summary

The KeyPress event in VB.NET is a useful event for handling input from the user while a control has focus. It allows you to enforce input validation and formatting for controls in a VB.NET application, and provides access to the pressed key through the e.KeyChar property of the KeyPressEventArgs object.